Aqueous inorganic oxidizer salt blasting compositions containing tamarind seed powder



United States Patent AQUEOUS INORGANIC OXIDHZER SALT BLAST- ENG COMPOSITIONS CONTAINING TAMARIND SEED POWDER Harry R. Fee, Hopatcong, N.J., John David Ferguson, Troy, N .Y., and Robert W. Lawrence, Wilmington, Del., assignors to Hercules Incorporated, a corporation of Deiaware No Drawing. Filed May 5, 1966, Ser. No. 547,734 9 Ciaims. (Ci. 149-60) This invention relates to inorganic oxidizer salt slurrytype blasting compositions containing tamarind seed powder as a thickener ingredient in either hydrated or crosslinked form and, when desired, as a sole carbonaceous fuel ingredient.

Inorganic oxidizer salt blasting compositions of the aqueous slurry type have had Wide use in the explosives industry in recent years. These compositions comprise an inorganic oxidizer salt, water, a sensitizer, and, generally, a thickening agent in at least an amount to impart sufficient consistency to the slurry to prevent settling of ingredients. Exemplary of these compositions are those disclosed and claimed in US. Patents 3,235,425 and 2,930,685.

Among the various thickeners that have been utilized in the past are sodium carboxymethyl cellulose, karaya gum, water-soluble starches, mannogalactans, locust bean gum, cereal products, and the like. Of these, perhaps guar gum has been the most widely used, particularly because it is easily hydrated and cross-linked to impart a degree of consistency, to the composition, over a broad range. However, cross-linkability of guar gum, in numerous instances, has been limited to acid systems often having a pH of 5.5 and less, the stability of cross-linked guar gum systems often being unsatisfactory, from a practical point of view, at the higher pHs. Further, the amount of guar gum utilized for requisite thickening is not generally sufficient for its function also as a sole carbonaceous fuel ingredient, when that is desired.

This invention is concerned with blasting compositions of the type above described, containing tamarind seed powder as the thickener ingredient over a broad range of acid and alkaline pHs and, when desired, as the sole carbonaceous ingredient.

In accordance with the invention, aqueous inorganic oxidizer salt slurry-type explosives are provided which contain a thickening amount, generally from about 1 to 10 weight percent or any suitable amount outside that range, of tamarind seed powder as a thickener component. The slurry compositions of the invention generally contain from 8 to 25 percent water, from about 30 to 75 percent oxidizer salt, from about 3 to about 50 percent sensitizer, and the above-described thickener.

By the term inorganic oxidizer salt, as is well known in the explosives art, is meant one which under the conditions of the detonation liberates oxygen for combustion of the fuel component.

Now preferred compositions of the invention contain (weight basis) from 12 to 20 percent water, from 40 to 60 percent ammonium nitrate, and from 5 to 20 percent so dium nitrate as the oxidizer salt, from 8 to 45 percent sensitizer and from about 1 to 4 percent tamarind seed powder.

Although ammonium nitrate alone, or with sodium nitrate, is in most instances the inorganic oxidizer salt component, other inorganic oxidizer salts can be used alone, or with ammonium nitrate as a supplemental oxidizer salt. Of these supplementary salts, the alkali metal nitrates are now preferred. Often when ammonium nitrate is utilized with a supplementary salt, it comprises a major proportion of the total oxidizer salt, i.e. at least50 3,35%,246 Patented Oct. 31, 1957 percent of the total. Exemplary inorganic oxidizer salts that can be used alone or together with ammonium nitrate are alkali metal (including ammonium) and alkaline earth metal nitrates and perchlorates as, for example, sodium nitrate, magnesium nitrate, calcium nitrate, potassium nitrate, barium nitrate, sodium perchlorate, ammonium perchlorate, calcium perchlorate, and magnesium perchlorate.

Any of the various known sensitizer materials for inorganic oxidizer salt blasting compositions of the aqueous slurry type, above described, can be utilized as such, in the compositions of the invention. Exemplary of now pre ferred sensitizer components are smokeless powder as disclosed and claimed in the above said US. 3,235,425 and TNT and/ or particulate aluminum as disclosed and claimed in the above said US. 2,930,685. Other suitable sensitizers include particulate magnesium-aluminum alloys, particulate ferrophosphorus, powdered coal, high explosive materials such as PETN and tetryl, and various carbohydrates.

Tamarind seed powder, the thickener component of the compositions of the invention, is a naturally occurring product of vegetable origin and is commercially available. It is often referred to as a fiour produced from the seed kernel of the tamarind tree (Tamarindus indica, Linn). A typical composition of the tamarind seed is 58.5 percent polysaccharide, 17.5 percent protein, 7.0 percent fats, 9.5 percent acid insolubles, 2.5 percent ash and 5.0 percent moisture. The polysaccharide component has been identified as being composed of D-galactose, D- xylose, and D-glucose in the molar ratios of about 1:2:3, respectively. The particular balance of materials in the natural tamarind seed is not critical in the practice of the invention. The tamarind seed is generally ground to a particle size such that at least 50 percent passes through a l00-mesh standard screen and in that form constitutes tamarind seed powder, the thickener component, the compositions of this invention.

Tamarind seed powder is present in the compositions of the invention in either hydra-ted or cross-linked form.

It does not absorb water as readily as, nor does it water swell to the extend of, that of most other thickeners that have been utilized in the above-described slurry explosives, particularly guar gum. Accordingly, the amount of tamarind seed powder generally utilized for hydration and cross-linking to accomplish a predetermined degree of consistency is generally greater than that required for other thickeners so that, in many such instances, the amount of tamarind seed powder present is sufficient for it to function also as a sole carbonaceous fuel ingredient.

Use of tamarind seed in a dual role as thickener and sole carbonaceous fuel ingredient eliminates handling and precautions often required when other carbonaceous fuels as, for example, a high explosive such as TNT and the like, are utilized in accordance with past practice.

It is generally advantageous to utilize the tamarind seed powder, in hydrated form, when it is necessary only to impart suitable thickening action during the mixing operation to retain all ingredients in suspension. However, the thickening action in that instance is somewhat limited; and, accordingly, when it is desired to impart a greater degree of consistency to the composition, it is generally preferred that the tamarind seed be present in cross-linked form. In those instances it is necessary that a suitable agent for cross-linking the tamarind seed powder be present.

When the tamarind seed powder thickener is utilized in hydrated form solely for the purpose of precluding settling of ingredients, an amount in the order of about 1 percent based on the total composition is usually sufficient. However, when it is desired to cross-link the tamarind seed for further regulation of consistency of (3 the composition, an amount of from 2 to 4 percent is usually employed, and in some instances up to about 7 percent. An amount of from 4 to 7 percent, and in some instances up to about 10 percent, is often advantageously applied to those formulations in which the tamarind seed powder is to function, both as a thickener and as sole carbonaceous fuel ingredient.

The tamarind seed component of the compositions of the invention can be cross-linked over a broad pH range. This is advantageous, particularly when utilizing certain energizers which impart pH conditions that are normally adverse to satisfactory hydration and/or cross-linking of other thickeners. For example, certain calcium compounds have been found to functiton satisfactorily as energizers in slurries of the type of which this invention is concerned. However, when endeavoring to utilize crosslinked guar gum as a thickener in a slurry, containing calcium boride as an energizer, the guar gum often fails to cross-link under the relatively high pH condition incurred, or if some cross-linking of the guar gum takes place, the resulting gel is so unstable that it breaks down, substantially completely, after a short period of time. On the other hand, in such a system, the tamarind seed thickener is readily cross-linked to form a resulting gel characterized by prolonged stability.

Any suitable mixing procedure can be utilized in the preparation of the compositions of the invention. In accordance with a now preferred embodiment the tamarind seed in its total contemplated amount and containing a cross-linking agent is dispersed in ethylene glycol and the resulting suspension is admixed with the Water ingredient at a temperature in the order of 130 to 160 F. under which conditions hydration takes place, with some thickening, sufficient to hold all ingredients in suspension. The oxidizer salt, a pH adjusting material, such as a suitable carboxylic acid, and remaining ingredients, including a sensitizer, are then admixed with the thickened water and tamarind seed admixture. Cross-linking to a substantial degree takes place within a period of from 2 to 5 hours, although some further cross-linking generally takes place over longer periods, say in the order of about to 12 hours.

When referring herein to hydration, it is meant the reaction that takes place between the tamarind seed powder and water components to form a sol, and when referring to cross-linking, it is meant the cross-linking that takes place between the tamarind seed powder and the particular cross-linking agent to form a gel.

Exemplary agents which function to promote crosslinking of tamarind seed powder in the process of the invention are those which liberate borate, cuprous, calcium, and aluminum ions, the cross-linking being promoted under pH conditions in the order of about 7 or somewhat higher. On the other hand, when the component mixture is acid, say having a pH in the order of 3 to 5, potassium pyroantimonate is advantageously utilized as a cross-linking agent. When utilizing Chile sodium nitrate, there is generally a sufficient amount of borate present as impurity, to promote the necessary cross-linking provided the pH of the system is in the order of about 7, as above described.

The compositions of the invention are in the most instances insensitive to a detonating action of a No. 8 commercial blasting cap but are, in all events, detonatable by conventional booster charges such as PETN (pentaerythritol tetranitrate), RDX (cyclotrimethylene trinitramine), Pentolite (PETN-TNT, 50/50), tetryl, Composition B (RDX-TNT, 60-40), and the like. One booster advantageously employed is a dispersion of a crystalline high explosive, e.g. PETN or RDX in a plastic carrier such as disclosed and claimed in US. 2,965,466 and which is detonatable by either a commercial blasting cap or a detonating fuse. A now preferred booster comprises a cast cylindrical body of capand fuse-insensitive explosive, and a tube assembly, within the cast body, containing 4 cap-sensitive crystalline high explosive together with structure for support of initiator means therefor, as disclosed and claimed in U.S. 3,212,438.

The invention is further illustrated with reference to the following formulations:

Guar Gum 1 Ammonium Nitrate Sodium Nitrate Smokeless Powder Sugar (Sucrose) Aluminum (Flaked) Calcium Boride Ethylene Glycol 5 Furnaric Acid pH Stability Detonation Rate, m./sec.

Crosslinked. Sodium borate, present as impurity in the sodium nitrate, as cross-linking agent-Runs 1, 2, and 4; potassium pyroantimohate, as cross-linking agent-Run 3 (0.3 pt.).

2 Prills, Run 3; granular, all others.

3 Naturally occurring Chilean sodium nitrateOoarse, Run 3; granular, all others.

4 20 mm. single base (0.1 x 0.04 grains, single perforation).

5 As carrier for guar gum and for tamarind seed powder in preparation of formulation.

6 For regulation of pH.

" Cross-linked, broke down after 2 hours.

3 Cross-linked, remained stable after 7 weeks.

9 Cross-linked, remained stable after 24 hours.

Measured as average detonation velocity over a 20 cm. length, at the end of a 28 long column of explosive. The explosive 1s confined in a 4 (Run 2) and a 5 (Run 3) diameter (nominal) black iron pipe (Schedule 40). The time for detonation to proceed across the 20 cm. length of explosive is measured electronically with a. counter-chronograph.

The examples illustrate tamarind seed powder as a thickener for aqueous slurry-type blasting compositlons in accordance with the invention. Example 1 illustrates an aqueous slurry composition containing calcium boride as an energizer and guar gum, as the thickener, crosslinked under the inherently resulting alkaline pH conditions. As shown, stability of the resulting gel (product of cross-linking) was poor, the gel breaking down after two hours. Example 2 illustrates a calcium boride-containing formulation about the same as that of Example 1, except for the presence of tamarind seed powder as the thickener cross-linked under the inherently resulting alkaline pH conditions. However, in that case, the resulting gel was stable after seven weeks. Example 3 illnstrates a formulation utilizing tamarind seed powder cross-linked under acid pH conditions, the resulting gel being stable for a period of at least 24 hours, there having been no further observation made after that time. Example 4 also illustrates tamarind seed powder in crosslinked form, not only as a thickener in accordance with the invention but also as a sole carbonaceous fuel ingredient.

Particle size and type of the oxidizer salt ingredients are generally not critical. For example, ammonium nitrate can consist of prills such as used in fertilizers and which are substantially all on 20 mesh, or it can be granular and in that form vary from coarse to fine. Other oxidizer salt ingredients are generally of comparable particle size. However, when desired, any or all of the oxidizer salt component can be added to the formulation, in aqueous solution.

As will be evident to those skilled in the art, various modifications can be made or followed in light of the foregoing disclosure and discussion, without departing from the spirit or scope of the claims.

What we claim and desire to protect by Letters Patent is:

1. In an inorganic oxidizer salt explosive of the aqueous slurry type, the improvement comprising a thickenll'lg amount of tamarind seed power as a thickener component.

2. A composition of claim 1 containing up to weight percent of said tamarind seed powder.

3. A composition of claim 2 containing from 1 to 7 percent of said tamarind seed powder.

4. A composition of claim 3 containing from '8 to 5 percent water, from to 75 percent of said inorganic oxidizer salt, and from 3 to percent of a sensitizer.

5. A composition of claim 4 containing at least 2 percent of said tamarind seed powder in cross-linked form.

6. An aqueous slurry-type composition of claim 5 containing from 12 to 20 percent water, from 40 to percent ammonium nitrate and from 5 to 20 percent sodium nitrate as the oxidizer salt, and up to 4 percent of said tamarind seed powder.

7. A composition of claim 4 containing ammonium nitrate as the only oxidizer salt.

8. A composition of claim 4 containing from 40 to 60 percent ammonium nitrate and from 5 to 20 percent sodium nitrate as the oxidizer salt.

9. A composition of claim 2 containing at least 4 percent of said tamarind seed in cross-linked form, and said tamarind seed constituting a sole carbonaceous fuel component.

References Cited UNITED STATES PATENTS 3,018,201 1/1962 Downard 149-60 X 3,160,538 12/1964 Zas-lowsky et a1. 149-60 X 10 3,214,307 10/1965 Logan et al. 149-46 X FOREIGN PATENTS 229,190 4/1959 Australia.

5 CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGE'IT, Examiner. S. J. LECHERT, JR., Assistant Examiner. 

1. IN AN INORGANIC OXIDIZER SALT EXPLOSIVE OF THE AQUEOUS SLURRY TYPE, THE IMPROVEMENT COMPRISING A THICKENING AMOUNT OF TAMARIND SEED POWER AS A THICKENER COMPONENT.
 2. A COMPOSITION OF CLAIM 1 CONTAINING UP TO 10 WEIGHT PERCENT OF SAID TAMARIND SEED POWDER.
 3. A COMPOSITION OF CLAIM 2 CONTAINING FROM 1 TO 7 PERCENT OF SAID TAMARIND SEED POWDER.
 4. A COMPOSITION OF CLAIM 3 CONTAINING FROM 8 TO 25 PERCENT WATER, FROM 30 TO 75 PERCENT OF SAID INORGANIC OXIDIZER SALT, AND FROM 3 TO 50 PERCENT OF A SENSITIZER.
 7. A COMPOSITION OF CLAIM 4 CONTAINING AMMONIUM NITRATE AS THE ONLY OXIDIZER SALT. 